With development of science and technology as well as market demand, a mobile phone having a metal housing is becoming more and more popular. The mobile phone having the metal housing has a beautiful appearance, but the metal housing may block radio signals from an antenna to some extent.
Currently, a gap area is defined in the metal housing by computer numerical control (CNC) machining, so as to enable transmission of the radio signals. Generally, a slot is defined in the metal housing by CNC machining, and then plastic is injected into the slot. However, the injecting pressure may be too great when injecting the plastic, such that the slot is pressed, deformed, and thus has a non-uniform width, which destroying appearance unity of the housing.